Technical Field
The present invention relates to an engine starter.
Related Art
A known technique for improving fuel economy of a vehicle is configured to torque-assist an engine via a motor so that both the engine and the motor serve as drive sources for driving the vehicle. Conventionally, a motor generator (MG) is used as such a motor.
However, the MG is an alternating-current (AC) motor, which suffers from disadvantages that the acceleration of the vehicle immediately after the start-up of the engine is delayed until detection of a rotational position of a rotor and that manufacturing costs are increased.
Therefore, it is desirable to have a technique for improving acceleration responsiveness immediately after the start-up of the engine.
An inexpensive vehicle-mounted motor including, but not limited to, a direct-current (DC) starter, may be used as a torque-assist motor.
Such a starter, however, suffers from discomfort caused by noise associated with driving the starter, such as an engagement sound between a ring gear and a pinion, and degradation of a drive-train between the starter and the engine, such as wear of the ring gear and the pinion. Thus, use of such a starter as a torque-assist motor needs overcoming these disadvantages.
Japanese Patent Application Laid-Open Publication No. 2008-190496 discloses a technique that enables evasive running of a vehicle via a starter using a DC motor, however, does not teach or suggest use of the starter for torque-assisting an engine. Japanese Patent Application Laid-Open Publication No. 2002-188549 discloses a starter capable of rotating up to speeds above an idle speed of an engine, however, does not teach or suggest use of the starter for torque-assisting an engine, either.
In consideration of the foregoing, exemplary embodiments of the present invention are directed to providing an engine starting apparatus capable of torque-assisting an engine via an inexpensive direct-current (DC) starter.